Method, wireless transmit/receive unit (wtru) and base station for transferring small packets

ABSTRACT

A method, a wireless transmit/receive unit (WTRU) and a base station for transferring small packets are described. The WTRU generates a packet that has one or more of a medium access control (MAC) or a physical layer convergence protocol (PLCP) header, the one or more of the MAC or the PLCP header including a field. On a condition that the WTRU has data buffered for transmission, the WTRU includes in the field information that indicates a time or a transmission opportunity (TXOP) needed to transmit at least one packet of data that the WTRU has buffered for transmission. The WTRU transmits the packet to another WTRU in the wireless network. The WTRU receives another packet from the other WTRU with a granted TXO) based on the time needed to transmit the at least one packet of the data that the WTRU has buffered for transmission.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/700,720 filed Sep. 13, 2012 and U.S. Provisional Application No.61/831,759 filed Jun. 6, 2013, the contents of which are herebyincorporated by reference herein.

BACKGROUND

A wireless local area network (WLAN) is a LAN that connects wirelessdevices or stations (STAs). In an infrastructure basic service set (BSS)mode, a WLAN includes an access point (AP) for the BSS and one or moreSTAs associated with the AP. The AP may have access, or an interface, toa distribution system (DS) or other type of wired or wireless networkthat carries traffic in and out of the BSS. Traffic originating fromoutside the BSS, but ultimately destined to a STA inside the BSS, mayarrive through the AP, which may deliver it to the appropriate STA.Similarly, traffic originating from STAs and destined to devices outsideof the BSS may be sent to the AP for delivery to the appropriate deviceoutside of the BSS. Traffic being exchanged between STAs in the BSS(also referred to as peer-to-peer traffic) may be sent via the AP or maybe transferred directly between source and destination STAs with adirect link setup (DLS) using an Institute of Electrical and ElectronicsEngineers (IEEE) 802.11e DLS or an IEEE 802.11z tunneled DLS (TDLS). Inan Independent BSS mode, a WLAN has no AP, and, therefore, STAs in anIndependent BSS mode communicate directly with each other.

Due at least to the nature and operation of at least some WLANS, WLANSTAs may need to transmit uplink (UL) small frames frequently. Such ULsmall frames may include, for example, power-save polls (PS-Polls),voice over internet protocol (VoIP) packets that may have medium accesscontrol (MAC) service data unit (MSDU) frames of around 120 bytes,industrial process automation in which frames may have an MSDU size ofaround 64 bytes, and packets that include data on web browsing clickingthat may have MSDU frames of around 64 bytes.

SUMMARY

A method, a wireless transmit/receive unit (WTRU) and a base station fortransferring small packets are described. The WTRU generates a packetthat has one or more of a medium access control (MAC) or a physicallayer convergence protocol (PLCP) header, the one or more of the MAC orthe PLCP header including a field. On a condition that the WTRU has databuffered for transmission, the WTRU includes in the field informationthat indicates a time needed to transmit at least one packet of datathat the WTRU has buffered for transmission. The WTRU transmits thepacket to another WTRU in the wireless network. The WTRU receivesanother packet from the other WTRU with a granted transmissionopportunity (TXOP) based on the time needed to transmit the at least onepacket of the data that the WTRU has buffered for transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingswherein:

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A;

FIG. 1C is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A;

FIG. 2 is a diagram of an example point coordination function (PCF)frame transfer;

FIG. 3 is a diagram of an example power-save multi-poll (PSMP)operation;

FIG. 4A is a flow diagram of an example method of transferring smallpackets;

FIG. 4B is a flow diagram of another example method of transferringsmall packets;

FIG. 5A is a diagram of an example method of transferring small packetsusing a variable-length frame check sequence (FCS);

FIG. 5B is a diagram of another example method of transferring smallpackets using a variable-length FCS;

FIG. 6 is a diagram of an example of group-based channel contention;

FIG. 7 is a diagram of another example of group-based channelcontention;

FIG. 8 is a diagram of another example of group-based channelcontention;

FIG. 9 is a diagram of an example Intra-CG transmission grant andsurrogate polling procedure; and

FIG. 10 is a diagram of an example inter-group transmission grant andsurrogate polling procedure.

DETAILED DESCRIPTION

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d may be configuredto transmit and/or receive wireless signals and may include userequipment (UE), a mobile station, a fixed or mobile subscriber unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,consumer electronics, a station (STA), an access point (AP) and thelike.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a Node-B, an eNode B,a Home Node B, a Home eNode B, a site controller, an access point (AP),a wireless router, and the like. While the base stations 114 a, 114 bare each depicted as a single element, it will be appreciated that thebase stations 114 a, 114 b may include any number of interconnected basestations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The cell may further be divided into cell sectors. For example,the cell associated with the base station 114 a may be divided intothree sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple-output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, etc.). Theair interface 116 may be established using any suitable radio accesstechnology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed DownlinkPacket Access (HSDPA) and/or High-Speed Uplink Packet Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface116 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106.

The RAN 104 may be in communication with the core network 106, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. For example, the core network 106may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the core network 106 may be in direct orindirect communication with other RANs that employ the same RAT as theRAN 104 or a different RAT. For example, in addition to being connectedto the RAN 104, which may be utilizing an E-UTRA radio technology, thecore network 106 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106 may also serve as a gateway for the WTRUs 102 a,102 b, 102 c, 102 d to access the PSTN 108, the Internet 110, and/orother networks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) andthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired or wireless communications networks ownedand/or operated by other service providers. For example, the networks112 may include another core network connected to one or more RANs,which may employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In another embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and receive both RF and light signals. It will be appreciatedthat the transmit/receive element 122 may be configured to transmitand/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 104 and the core network 106according to an embodiment. The RAN 104 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 116. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 104, andthe core network 106 may be defined as reference points.

As shown in FIG. 1C, the RAN 104 may include base stations 140 a, 140 b,140 c, and an ASN gateway 142, though it will be appreciated that theRAN 104 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 140 a, 140 b,140 c may each be associated with a particular cell (not shown) in theRAN 104 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 116. In oneembodiment, the base stations 140 a, 140 b, 140 c may implement MIMOtechnology. Thus, the base station 140 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 140 a, 140 b, 140 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 142 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 106, and the like.

The air interface 116 between the WTRUs 102 a, 102 b, 102 c and the RAN104 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 106.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 106 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 140 a, 140 b,140 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 140 a, 140 b,140 c and the ASN gateway 215 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 100 c.

As shown in FIG. 1C, the RAN 104 may be connected to the core network106. The communication link between the RAN 104 and the core network 106may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 106 may include a mobile IP home agent(MIP-HA) 144, an authentication, authorization, accounting (AAA) server146, and a gateway 148. While each of the foregoing elements aredepicted as part of the core network 106, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 144 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 146 may be responsible for userauthentication and for supporting user services. The gateway 148 mayfacilitate interworking with other networks. For example, the gateway148 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 148 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1C, it will be appreciated that the RAN 104may be connected to other ASNs and the core network 106 may be connectedto other core networks. The communication link between the RAN 104 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 104 and the other ASNs. The communication link betweenthe core network 106 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

Other network 112 may further be connected to an IEEE 802.11 basedwireless local area network (WLAN) 160. The WLAN 160 may include anaccess router 165. The access router may contain gateway functionality.The access router 165 may be in communication with a plurality of accesspoints (APs) 170 a, 170 b. The communication between access router 165and APs 170 a, 170 b may be via wired Ethernet (IEEE 802.3 standards),or any type of wireless communication protocol. AP 170 a is in wirelesscommunication over an air interface with WTRU 102 d.

As described above, for at least some WLAN systems, WLAN STAs may needto transmit UL small frames frequently. Some more specific examples ofsuch WLAN systems follow, in particular, as related to pointcoordination function (PCF), quality of service (QoS) hybridcoordination function controlled channel access (HCCA), power-savemulti-poll (PSMP) and WLAN operation in spectrum allocated below 1 GHz(the Sub 1 GHz spectrum).

PCF is a technique that may be used in IEEE 802.11-based wireless localarea networks (WLANs) whereby a point coordinator (PC) AP coordinatescontention-free (CF) frame transfer within the network. PCF CF frametransfer may be based on a polling scheme, which may be controlled by aPC operating at the AP of the BSS.

FIG. 2 is a diagram of an example PCF frame transfer 200. The examplePCF frame transfer 200 illustrated in FIG. 2 includes a contention-freerepetition interval 202, which includes a contention-free period (CFP)204 followed by a contention period 212. In an embodiment of PCF, thecontention-free repetition interval 202 may be repeated to providecontention-free and contention-based access to a wireless medium over aperiod of time.

A PC may initiate a CFP 204 by including a CF parameter set element in abeacon 214. Every station that receives the beacon 214 may set their NAV206 to the nominal start time of each CFP 204 to prevent non-polledtransmissions.

The PC may poll CF-pollable STAs for UL transmissions using poll frames.In the example illustrated in FIG. 2, the PC waits a short interframespace (SIFS) period 210 a after the beacon 214 to transmit its firstpoll frame 216. In an embodiment, the PC may use any one of a number ofdifferent frames as the poll frame, including, for example, aData+CF-Poll frame, a Data+CF-ACK+CF-Poll frame or a CF-Poll frame. Useof these different types of poll frames may enable the PC to efficientlyuse poll frames to also transmit other data it has for transmission. Forexample, the PC may use the Data+CF-Poll frame to transmit DL data withthe Poll frame if it has DL data to transmit. For another example, thePC may use the Data+CF-ACK+CF-Poll frame to transmit DL data and anacknowledgement (ACK) if it has DL data and an ACK to transmit. If thePC has no other data to transmit, it may simply transmit a CF-Pollframe. Acknowledgement of frames sent during a CFP (e.g., CFP 204) maybe accomplished using one of Data+CF-ACK, CF_ACK, Data+CF-ACK+CF-Poll,or CF-ACK+CF-Poll frames if a data or null frame immediately follows theframe being acknowledged, thereby avoiding the overhead of separate ACKframes.

In response to being polled, a CF-Pollable STA may transmit UL frameswithout contention after a SIFS period. This may provide a higherutilization of the medium than for transmissions made under adistributed coordination function (DCF). In the example illustrated inFIG. 2, after the PC transmits the first poll frame 216, the polled STAwaits a SIFS period 210 b and then transmits one or more UL frames 218.After another SIFS period 210 c, the PC may transmit its next poll frame220, and after another SIFS period 210 d, the polled STA may transmitone or more UL frames 222. After another SIFS period 210 e, the PC maytransmit its next poll frame 224. On a condition that the PC does notreceive a response to the poll frame 224 within a priority interframespace (PIFS) period 208 b, the PC may transmit its next poll frame 226.After another SIFS period 210 f, the STA being polled may transmit oneor more UL frames 228.

Once the PC has polled all of the STAs in the BSS, the PC may wait aSIFS period 210 g and then transmit a CF-End frame 230 to indicate theend of the CFP 204. In response to receiving the CF-End frame 230, STAsmay reset their NAVs 232, and the contention period 212 may begin. Afterthe contention period 212, the PC may wait a SIFS period (e.g., SIFSperiod 208 a) before initiating the next CF period, for example, byincluding a CF parameter set element in the beacon.

IEEE 802.11e systems may use an HCCA procedure to control channel accessusing a centralized controller. While both PCF and HCCA use centralizedcontrol to control channel access, HCCA and PCF are different at leastin that HCCA may take place in both a CP or CFP and an HCCA STA may begranted a polled TXOP with the duration specified in a QoS(+)CF-Pollframe. STAs may transmit multiple frame exchange sequences within agiven polled TXOP subject to the limit of the TXOP duration.

IEEE 802.11n systems may use a power-save multi-poll (PSMP) mechanismwherein a single PSMP frame may be used to schedule multiple STAsinstead of using the direct QoS(+)CF-Poll used in HCCA. The PSMP may bemore efficient than the QoS(+)CF-Poll in situations where STAs need totransmit a small amount of data periodically.

FIG. 3 is a diagram of an example PSMP operation 300 for three STAs. Inthe example PSMP operation illustrated in FIG. 3, an AP 322 transmits aPSMP frame 306 that may be received by all of the STAS 324, 326 and 328in the BSS. The AP may include in the PSMP frame 306 a scheduleindicating to the STAs when they need to be awake to receive DL dataframes during a DL phase 302 and the individual times at which each STAis allowed to begin transmitting UL data during a UL phase 304. In theexample illustrated in FIG. 3, the DL phase 302 includes a broadcastperiod 308 followed by DL periods 310, 312 and 314 during which each ofthe respective STAs 324, 326 and 328 may receive DL data. The example ULphase 304 includes UL periods 316, 318 and 320 during which the STAs324, 326 and 328 may respectively make UL transmissions.

Use of PSMP may reduce power consumption by STAs by providing the UL andDL schedule at the start of the PSMP phase so that each STA may shutdown its receivers until needed in the DL phase and transmit only whenscheduled during the UL phase without need to perform a clear channelassessment (CCA).

Some WLAN systems (e.g., WLAN systems built on the IEEE 802.11 Standard)are designed to operate in the Sub 1 GHz spectrum. Such spectrum may bequite limited in the size and bandwidth of the channels they comprise.In addition, such spectrum may be fragmented in that available channelsmay not be adjacent and may not be combined for larger bandwidthtransmissions. Given the limitations of such spectrum, WLAN systemsoperating in it may only be able to support smaller bandwidths and lowerdata rates compared to high throughput/very high throughput (HT/VHT)WLAN systems (such as WLAN systems based on the IEEE 802.11n and/or802.11ac Standards).

With respect to IEEE 802.11ah systems operable in Sub 1 GHz bands, anOFDM physical layer (PHY) that is operable below 1 GHz in license-exemptbands excluding the television white space (TVWS) band may be desirable.Further, enhancements to MAC may be desirable to supply PHY andcoexistence with other systems (e.g., IEEE 802.15.4 and IEEE P802.15.4gsystems). Even further, it may be desirable to optimize rate versusrange performance (e.g., range of up to 1 km (outdoor)) and data ratesgreater than 100 Kbit/s). Three use cases have been considered,including sensors and meters, backhaul sensor and meter data andextended range WiFi for cellular offloading.

Spectrum allocation in some countries may be quite limited. For example,in China, the 470-566 and 614-787 MHz band may only allow a 1 MHzbandwidth spectrum allocation. It may be desirable to support a 1 MHzonly option in addition to supporting a 2 MHz option with a 1 MHz mode.

The IEEE 802.11ah PHY may operate below 1 GHz and is based on the IEEE802.11ac PHY. To accommodate the narrow bandwidths required by IEEE802.11ah, the IEEE 802.11ac PHY may be down-clocked by a factor of 10.While support for 2, 4, 8 and 16 MHz may be achieved by 1/10down-clocking, support for the 1 MHz bandwidth may require a PHYdefinition with a Fast Fourier Transform (FFT) size of 32.

The IEEE 802.11ah sensors and meters use case requires support for up to6,000 STAs within a single BSS. Devices such as smart meters and sensorshave very different requirements pertaining to supported UL and DLtraffic. For example, sensors and meters may be configured toperiodically upload their data to a server, which will most likely be ULtraffic only. Sensors and meters may also be queried or configured bythe server. When a server queries or configures a sensor and meter, itmay expect that the queried data should arrive within a set up interval.Similarly, the server/application may expect a confirmation for anyconfiguration performed within a certain interval. These types oftraffic patterns may be very different than traditional traffic patternsassumed for WLAN systems.

In the above examples, STAs, for example, may need to frequentlytransmit UL small frames including, for example, PS-Polls, industrialprocess automation (in which the frames may have an MSDU size of 64bytes), web browsing clicking (in which the frames may have an MSDU sizeof 64 bytes) and VoIP (in which the frames may have an MSDU size of 64bytes).

Further, a set of STAs may be scheduled to conduct medium access duringa beacon interval, a beacon sub-interval or a time interval. IfDCF-based access is used, much overhead may be associated with thetransmission of UL packets, including DCF interframe space (DIFS),backoff, packet collisions and retransmission. The overhead may beparticularly severe for small UL frames. If a contention-free method ofUL transmission is used (e.g., where each STA is assigned a time slot totransmit their packets), there may not be much overhead since some STAsmay have UL data packets to transmit while other STAs may simplytransmit a PS-Poll frame to retrieve their buffered DL frames. Someportions of the assigned slots may remain idle after a STA completes itstransmission until the start of the next time slot. These portions ofassigned slots may, therefore, be wasted.

A set of STAs may be scheduled to conduct medium access in a beaconinterval, beacon sub-interval or a given time interval in at least oneof several ways. The AP may instruct the STAs to wake up during acertain interval using a management or control frame. An AP may includea positive traffic indication map (TIM) in its beacon or short beaconfor STAs that transmit UL PS-Poll frames to retrieve their DL bufferedpackets. An AP may also include in its beacon indications of IDs,classes or other indicators of sets of STAs that are allowed to access acertain interval to conduct UL transmissions.

Speed frame exchange mechanisms have also been considered for IEEE802.11. For example, a STA may indicate the presence of UL data usingthe more data field in the MAC header. For another example, for eitherUL or DL transmissions, a data frame may be used as a valid responseframe. For another example, early ACK indication bits in the PLCP headermay be used to indicate a medium reservation time associated withtransmission of the data frame as a response frame to the current frame.

When a BSS includes a large number of STAs with bursty uplink (UL)traffic, a lot of overhead may be associated with the transmission anddelivery of the UL packets. Some of this overhead may include thetransmission of PHY convergence protocol (PLCP) and MAC headers, framecheck sequences (FCSs), request to send (RTS)/clear to send (CTS) andacknowledgement (ACK) frames, time that a STA must wait to gain channelaccess (e.g., DIFS and backoff countdown), and retransmissions due tocollisions. Overhead associated with transmitting data or a frame, suchas a PS-Poll, that is short in length, may be particularly pronouncedbecause the time associated with the transmission overhead may beseveral times longer than the actual transmission time of the data orpacket itself. Consequently, a WLAN system may use significant resourcesto transmit the overhead and, thus, have low MAC efficiency.Accordingly, mechanisms may be desirable to reduce overhead and toimprove MAC efficiency in WLAN systems.

Embodiments are described herein that may reduce overhead associatedwith transferring small data packets. In an embodiment, a wirelesstransmit/receive unit (WTRU), such as a STA, may transmit more detailedinformation about a packet it has for transfer, which may provide forhigher MAC and power efficiency. In another embodiment, a frame checksequence (FCS) of variable length may be used, the dynamic length of theFCS depending, for example, on the length of the frame body in order tominimize overhead associated with transmission of UL small data frames.In another embodiment, WTRUs may use group-based channel contention toaccess the medium.

FIG. 4A is a flow diagram 400A of an example method of transferringsmall packets, for example, in a wireless network, such as a WLAN. Inthe example illustrated in FIG. 4A, a WTRU, such as a STA, generates apacket that has a MAC header with a field that indicates that the WTRUhas data buffered for transmission (402). The WTRU may include a fieldin the packet (e.g., in the MAC or PHY layer convergence procedure(PLCP) header) that provides more detailed information about the datathat the WTRU has buffered for transmission (404).

The WTRU may indicate that it has data buffered for transmission using,for example, the More Data Field, in an MAC (e.g., an IEEE 802.11 MAC)or PLCP header. In an embodiment, the WTRU may include a bit in the MoreData Field that indicates that the WTRU has data buffered fortransmission. The more detailed information about the data that the WTRUhas buffered for transmission may be indicated, for example, as aninformation element (IE) (e.g., buffered traffic IE), or in the MAC/PLCPheader, as initial scrambling seeds or as a field or subfield (e.g., thebuffered traffic indication field or subfield) of any management,control, data, or other type of frame. The more detailed informationabout the data that the WTRU has buffered for transmission may also beindicated, for example, by reusing any field or subfield, such as all ora subfield of the QoS control field in the MAC header.

In an embodiment, the WTRU may transmit the more detailed information toanother WTRU or a base station (e.g., an AP), which may use the moredetailed information to enable more efficient small packet transmission,for example, by assigning transmission opportunities (TXOPs) to WTRUsbased on the more detailed information provided by WTRUs (e.g., STAs inthe BSS).

The more detailed information about the data that the WTRU has bufferedfor transmission may include, for example, one or more of a timerequired for transmission of at least one packet that the WTRU hasbuffered for transmission, a number of packets that the WTRU hasbuffered for transmission, a size of each of the packets (e.g., inbytes) that the WTRU has buffered for transmission, or a total size ofall of the packets that the WTRU has buffered for transmission. The timeneeded to transmit at least one packet of the data that the WTRU hasbuffered for transmission may include, for example, at least one of theestimated time or TXOP needed for the WTRU to transmit each packet thatthe WTRU has buffered for transmission or a total time or TXOP neededfor the WTRU to transmit all of the UL or DL packets the WTRU hasbuffered for transmission (e.g., in microseconds or any other timeunit).

FIG. 4B is a flow diagram 400B of another example method of transferringsmall packets, for example, in a wireless network, such as a WLAN. Inthe example illustrated in FIG. 4B, a WTRU (e.g., a STA) generates apacket that has a MAC header with a field that indicates that the WTRUhas data buffered for transmission and a field that indicates a timeneeded to transmit at least one packet of the data that the WTRU hasbuffered for transmission (410). The WTRU may transmit the packet toanother WTRU (e.g., an access point (AP)) in the wireless network (412).The WTRU may receive another packet from the other WTRU with a grantedtransmission opportunity (TXOP) based on the time needed to transmit theat least one packet of the data that the WTRU has buffered fortransmission (414).

In an embodiment, the granted TXOP has a duration that is based on thetime provided in the MAC header of the packet. The packet may be one ofa power-save poll (PS-Poll) frame, an ACK frame, a data frame and ablock acknowledgement (BA) frame.

In an embodiment, the WTRU may use new frame formats that include thebuffered traffic indication field. Such new frame formats may include,for example, a PS-Poll+Buffered Traffic (BT) frame format, an ACK+BTframe format, a Data+BT frame format, a short ACK+BT frame format, aBA+BT frame format, or a short BA+BT frame format. In anotherembodiment, a bit may be used to indicate the presence of the bufferedtraffic indication field in the PLCP/MAC header or in any other part ofany frame, such as a PS-Poll frame, an ACK frame, a data frame, a BAframe, a short ACK frame or a short BA frame. A buffered trafficindication field may also be included in, for example, PLCP tail bits orinitial scrambling seeds of new or existing frames. In an embodiment,the more data bit in the UL/DL direction may be set to indicate thepresence of a buffered traffic indication field.

The buffered traffic indication field may include detailed informationabout one or more of UL or DL traffic buffered at the transmitting WTRU.If the transmitting WTRU is a non-AP STA and the destination of thepacket is the AP, then the buffered traffic indication field may be usedto indicate the detailed information about the buffered UL packets. Ifthe transmitting WTRU is an AP and the destination of the packet is anon-AP STA, then the buffered traffic indication field may be used toindicate the detailed information about buffered DL packets. If thetransmitting WTRU is a non-AP STA and the destination of the packet is anon-AP STA, then the buffered traffic indication field may be used toindicate the detailed information on buffered peer-to-peer packets. Thebuffered traffic indication field may also be used to indicate thedetailed information on buffered broadcast or multicast packets for aparticular set of STAs.

For frames such as PS-Poll, ACK, data and BA frames for an 802.11ah STA,one bit in the PLCP/MAC header (e.g., in the frame control field or theMore Data field) may be used to indicate the presence of a bufferedtraffic indication field or sub-field. Such an indication may also beincluded, for example, in the PLCP tail bits or initial scramblingseeds. The buffered traffic indication field may include detailedinformation on buffered DL and/or UL packets, such as described above.Further, the buffered traffic indication field may be implemented as awhole field, or a subfield of, the QoS control field.

In an embodiment, a WTRU (e.g., a STA) that, for example, has received apositive TIM indication or has woken up from a sleep state and hasobtained access to the medium, may transmit a data frame with a bufferedtraffic indication field if the WTRU has UL data to transmit. Here, thepresence of a buffered traffic indication field may be indicated by aMore Data bit. In an embodiment, the WTRU may wake up from a sleep stateand, in response to waking up from the sleep state, transmit a PS-Pollframe with buffered traffic indication field, on a condition that theWTRU has UL data to transmit. Here, the presence of a buffered trafficindication field may be indicated by the More Data bit. The WTRU maytransmit a PS-Poll frame without a buffered traffic indication field (ora buffered traffic indication field indicating 0 buffered packets) ifthe WTRU has no UL data to transmit. In an embodiment, the WTRU maytransmit an aggregated MPDU (A-MPDU) or an aggregated MSDU (A-MSDU) thatincludes any combination of PS-Poll and data frames and a new type offrame that includes the buffered traffic indication field/IE.

Another WTRU or base station (e.g., an AP or another STA) may thenperform one of the following. The other WTRU may transmit a data framewith a granted TXOP (e.g., in the duration field or in a subfield of theQoS control field in the MAC header) to the WTRU for UL onlytransmissions or for both UL and DL transmissions (when the other WTRUis an AP that also has DL packets to transmit) when receiving a dataframe with a buffered traffic indication field. The data frametransmitted by the other WTRU may also include a buffered trafficindication field for any buffered DL packets at the other WTRU destinedfor the WTRU. The other WTRU may transmit an ACK/BA frame with a grantedTXOP (e.g., in the duration field of the MAC header or the ACK/BA mayinclude, or may be a subfield of, the QoS Control field in the MACheader for this purpose) to the WTRU for UL only transmissions or bothUL and DL transmissions (when the AP also has DL packets to transmit)when receiving a data frame with a buffered traffic indication field.The ACK/BA frame transmitted by the other WTRU may also include abuffered traffic indication field for any buffered DL packets at theother WTRU destined for the WTRU. The other WTRU may transmit an A-MPDUor an A-MSDU that includes any combination of data frames, ACK/BA or anya new type of frame that includes either the granted TXOP or thebuffered traffic indication field/IE for DL packets. The A-MPDU orA-MSDU may also include the information on the granted TXOP in itsduration or QoS control field in the MAC header or any other field orsubfieldsAll other WTRUs that receive the frames with the granted TXOPmay go to sleep until the end of the TXOP for energy conservation. Theother WTRU may also include schedule information on the granted TXOP,such as in the form of a Restricted Access Window (RAW) slot or a TargetWake Time (TWT), in any field or subfield of a packet such as in theMAC/PLCP header or in an RPS element.

In response to receiving the TXOP to transmit its UL frame, the WTRU mayuse the TXOP to complete its UL transmissions using any allowabletransmission sequence, such as data frames, A-MPDUs, or A-MSDUs, with orwithout immediate ACK/BA. The other WTRU may acknowledge the receptionsof these UL packets using ACK, short ACK, BA, short BA or data framesaccording to agreed ACK policies. At the end of its transmissions, theWTRU may transmit a CF-End frame to cancel its TXOP if there issufficient time for the transmission of the CF-End frame. The other WTRU(e.g., an AP) may repeat the CF-End frame if it does not have any DLframes to transmit to the WTRU. The other WTRU it may also starttransmitting the DL packets to the WTRU or any other WTRUs after a SIFSperiod from the CF-End frame.

In another embodiment, a WTRU (e.g., a STA) may have received a positiveTIM indication or may wake up from a sleep state (e.g., at its targetwake time (TWT)). When the WTRU obtains access to the medium, it maytransmit a data frame with a buffered traffic indication field if theSTA has UL data to transmit. The presence of a buffered trafficindication field may be indicated by the more data bit or other type ofindication. The WTRU may transmit a PS-Poll frame, an NDP PS-Poll frame,or another type of trigger frame, with buffered traffic indicationfield, if the STA has UL data to transmit. The presence of the bufferedtraffic indication field may be indicated by the more data bit or othertype of indication. The WTRU may transmit a PS-Poll frame without abuffered traffic indication field (or a buffered traffic indicationfield indicating 0 buffered packet) if the STA has no UL data totransmit. The WTRU may transmit an A-MPDU or A-MSDU including anycombination of PS-Poll frames, data frames and/or a new type of framethat includes the buffered traffic indication field/IE.

A WTRU (e.g., an AP or another STA) that is the destination of theframe(s) transmitted by the STA may then transmit a data frame with agranted TXOP (e.g., in the Duration, in a subfield of the QoS Controlfield in the MAC header, or in another part of the PLCP/MAC header,frame body, etc.) to the STA for UL only transmissions, or for both ULand DL transmission (when the AP also has DL packets to transmit) whenreceiving a frame with a buffered traffic indication field. The he Dataframe transmitted by the AP may also include a buffered trafficindication field for any buffered DL packets at the AP for the STA. Thegranted TXOP may be for the transmission of one UL and/or DL frame only.For example, the granted TXOP may be the TXOP for the transmission ofone MSDU, which may be implemented as MAX_PPUD_Time.

The WTRU may transmit an ACK/BA frame with a granted TXOP (e.g., in theDuration Field of the MAC header, in another part of the PLCP/MAC headeror frame body, or, alternatively, the ACK/BA may include a subfield ofthe QoS Control field in the MAC header for this purpose) to the STA forUL only transmissions or for both UL and DL transmissions (when the APalso has DL packets to transmit) when receiving a frame with a bufferedtraffic indication field. The ACK/BA frame transmitted by the AP mayalso include a buffered traffic indication field for any buffered DLpackets at the AP for the STA. The granted TXOP may be for thetransmission of one UL and/or DL frame only. For example, the grantedTXOP may be the TXOP for the transmission of one MSDU, which may beimplemented as a MAX_PPUD_Time.

The WTRU may transmit an A-MPDU or A-MSDU including any combination ofdata frames, ACK/BA frames or any a new type of frame that includeseither the granted TXOP or the buffered traffic indication field/IE forDL packets. The A-MPDU or A-MSDU may also include the information on thegranted TXOP in its duration or QoS control field in the MAC header orany other field or subfields. The WTRU may transmit a deferral packet,which may be a control, action, action without ACK frame, management orextension frame to inform the STA that one or more RAW/TWT/AccessWindow/Beacon interval/Beacon Sub-intervals is reserved for the STA, andthe STA may need to be active during that period(s) of time to completethe UL transmission and/or DL reception. This may be because the amountof UL and/or DL traffic associated with the STA is large and may not becompletely transmitted within the allocated slot/accesswindow/RAW/Beacon (sub)interval so that additional slot(s)/TWT(s)/accesswindow(s)/RAW(s)/Beacon (sub)interval(s) may need to be allocated. Sucha frame may be implemented using a resource allocation frame, S1GAction/Extension frame, or any control, management, data, or extensionor other type of frame, which may use RAW, TWT, or other type ofscheduling IE and field/subfield for this purpose. Alternatively, the APand STA may transmit their frame exchanges as normal, and the AP maytransmit the deferral packet to the STA at the end of the currentslot/TWT/access window/RAW/Beacon (sub)interval so that the AP and theSTA may complete their UL and/or DL transmissions in a newslot/TWT/access window/RAW/Beacon (sub)interval.

All other STAs that receive the frames with the granted TXOP may go tosleep until the end of the TXOP for energy conservation. The STA, uponreceiving the TXOP to transmit its UL frame, may then use the TXOP tocomplete its UL transmissions using any allowable transmissionsequences, such as data frames, A-MPDUs, or A-MSDUs, with or withoutimmediate ACK/BA. Any frames transmitted by the STA may includeadditional buffered traffic indication fields with updated informationon the amount of buffered UL traffic, which may take into account anybuffered UL information that has been transmitted/successfully deliveredas well as any packets that newly arrived for UL transmission.

The AP may acknowledge the receptions of these UL packets using ACK,short ACK, BA or short BA, data according to the agreed ACK policies.Similarly as for the STA, the frames transmitted by the AP may includeadditional buffered traffic indication fields with updated informationon the amount of buffered DL traffic, which may take into account anybuffered DL information that has been transmitted/successfully deliveredas well as any packets that newly arrived for DL transmission.

The STA, at the end of its transmissions, may transmit a CF-End frame tocancel its TXOP if there is sufficient time for the transmission of theCF-End frame. The AP may repeat the CF-End frame if it does not have anyDL frames to transmit to the STA. It may also start transmitting the DLpackets to the STA or any other STAs after a SIFS time from the CF-Endframe.

If the STA has received a deferral frame from the AP instructing it touse a different slot(s)/TWT(s)/access window(s)/RAW(s)/Beacon(sub)interval(s) for its UL and/or DL traffic, it may sleep until thattime. Once it wakes up, it may follow the channel access policyaccording to the AP's instructions to access the channel. The STA maystart the frame exchange sequence using a PS-Poll, NDP PS-Poll, or anyother type of trigger frame, such as data, which may include a bufferedtraffic indication field. The AP may start the frame exchange sequenceusing any type of frames, such as data, control, management or extensionframes, which may also include a buffered traffic indication field.

In another embodiment, a frame check sequence (FCS) of variable lengthmay be used, the dynamic length of the FCS depending, for example, onthe length of the frame body in order to minimize overhead associatedwith transmission of UL small data frames. A standard FCS field may be 4bytes long, which may not always be necessary for short frames.Accordingly, use of a dynamic FCS field may reduce transmission overheadassociated with a packet or frame that is short in length.

The length of the FCS field, as well as the design of the FCS field, maybe indicated in the PLCP/MAC header (e.g., in the SIG, SIGA and/or SIGBfield of the PLCP header or in the frame control field in the MACheader), may be included in the initial scrambler seed or may beimplicitly defined. With reference to FIG. 4B, in an embodiment, thepacket generated by the WTRU in 402 may further include a field thatindicates a length of a dynamic FCS field that is included in thepacket. In an embodiment, the length of the field may be indicated inthe PLCP/MAC header as a number of bytes (e.g., 1-N). For example, theFCS field may have a length that is less than 4 bytes. The design of theFCS field may be a new FCS using a new polynomial or may be puncturedfrom the existing FCS sequence as well as puncture rate.

In addition, the use of a short/dynamic FCS length for a frame may bepre-negotiated by either single user frame compression procedures orintra-group data/frame compression procedures. The length of the FCSfield and the type of FCS construction may be abstracted as a part ofthe specification of a particular compressed data/frame type between atransmitting and a receiving STA or among a group of STAs. The type ofcompressed data/frame with a particular FCS length or construction orother properties may be indicated in the PLCP/MAC header (for example inthe SIG, SIGA and SIGB field of the PLCP header or in the frame controlfield in the MAC header), by the initial scrambler seed or it isimplicitly defined.

A WTRU may indicate that it has the capability of using a dynamic FCSfield length in, for example, the capability field or any other field,subfield or IE included in the beacon. Or the WTRU may indicate itscapability for dynamic FCS field length in Probe Request and ProbeResponse frames, Association Request and (Re)Association Responseframes, or any other type of management, control or extension frames.The capability of using dynamic FCS length may be exchanged at the timeof association and at any other times. The usage of dynamic FCS lengthor shortened FCS length in a particular frame may be indicated by one ormore bits in the PLCP header.

In response to receiving a frame that indicates that the frame hasdynamic FCS, the receiving WTRU (e.g., STA) may obtain the FCS fieldaccording to the FCS length specified, check the correctness of theframe and decide to either discard the frame as incorrectly received orrelay the frame to higher layers. If the FCS specification ispre-negotiated (e.g., using a single user or group data/framecompression procedure), then the receiving WTRU may search for apre-negotiated record for FCS specifications associated with theparticular type of compressed data/frame.

FIG. 5A is a diagram of an example method 500A of transferring smallpackets using a variable-length FCS. In the example illustrated in FIG.5A, a WTRU (e.g., a STA) generates a frame that has an FCS and a PLCPand/or MAC header that indicates a length of the FCS (502). The lengthof the FCS may be variable. The WTRU may then transmit the packet toanother WTRU (e.g., a different STA or an AP) (504).

FIG. 5B is a diagram of another example method 500B of transferringsmall packets using a variable-length FCS. In the example illustrated inFIG. 5B, a WTRU or base station (e.g., an AP or a STA) receives a frame(e.g., from another WTRU such as another AP or STA) that has an FCS anda PLCP and/or MAC header that indicates a length of the FCS (510). Thelength of the FCS may be variable. The WTRU or base station may obtainthe FCS field from the packet using the length indicated in the PLCPand/or MAC header (512). The WTRU or base station may check thecorrectness of the frame using the FCS field obtained from the packet(514). On a condition that the WTRU or base station determines that theframe is correct (516), the WTRU or base station may relay the frame tohigher layers (520). On a condition that the WTRU or base stationdetermines that the frame is not correct, the WTRU or base station maydiscard the frame (518).

In an embodiment, WTRUs may use group-based channel contention to accessthe medium. Here, STA-to-STA grants may be provided for medium accessfor UL transmissions in order to minimize overhead associated withtransmitting UL small data frames.

In group-based channel contention, the set of WTRUs (e.g., STAs) thatare allowed to conduct UL transmissions (e.g., PS-Polls, data frames orother types of frames) may be divided into one or more groups referredto as contention groups (CGs). Accordingly, instead of each individualWTRU competing for the channel, for example, one WTRU in each of the CGsmay be selected to conduct channel contention for the CG. For example,if 20 STAs are scheduled to conduct UL medium access in an interval, theset of 20 STAs may be divided into five CGs of four STAs each. One STAin each of the five CGs may be selected to be the contender for the CGand is responsible for starting medium access for the entire CG. Thus,instead of 20 STAs competing for medium access, only five contenders maycompete for medium access, which may significantly reduce theprobability of collision and retransmissions. Once a contender of a CGgains access to the medium, it may be implicit that the entire CG gainsaccess to the medium, and the transmission period for that CG maycommence.

In addition, the group-based contention may have the added benefit ofpotentially reducing the amount of UL transmissions in event-drivenSTAs. For example, if some fire sensors located in the same geographicalarea are grouped into a CG, and if the contender has gained access tothe channel and transmitted its packet reporting an event (e.g., eithera fire has been detected or has not been detected), the other STAs inthe same CG may send a compressed version of a frame to report that theyare reporting the same data. In this way, the medium occupation timecaused by STAs in the CG transmitting frames may be significantlyreduced, in addition to the reducing collisions and retransmissions.

The role of CG contender may be assigned to a WTRU in a contention groupin at least one of several ways. In an embodiment, a base station orWTRU, such as an AP, may assign a WTRU, such as a STA, in a CG to be thecontender, either explicitly in a management, control or other type offrame or implicitly (e.g., implied by a positive TIM indication). Forexample, an AP may pre-negotiate with STAs that positive TIM indicationsmay be divided into several CGs with each CG including N STAs. The NSTAs that are associated with the first N positive TIM indications maybe in CG1, and the STA that is associated with the first positive TIMindication may be the contender for CG1. Similarly, the next N STAs thatare associated with the (N+1)^(th) to the 2N^(th) positive TIMindications may be in CG2, and the STA that is associated with the(N+1)^(th) positive TIM indication may be the contender for CG2.

In another embodiment, a CG may have a particular STA assigned to be itscontender all the time. Alternatively, the STAs in a CG may rotate totake on the role of the contender of the CG. Here, the STAs may follow apre-determined order to become the contender (e.g., the order of the MACaddresses or association IDs (AIDs) for the STAs). In anotherembodiment, a contender may explicitly hand over the role of thecontender to another STA in the CG.

When competing for the CG, the contender may use one or more of adifferent access category or a different set of enhanced distributedchannel access (EDCA) parameters. For example, new access categories maybe defined for group contention, which may have higher priorities thanSTA-based access categories. Such new access categories may includeAC_GP_VO (group access category for voice traffic), AC_GP_VI (groupaccess category for video traffic), AC_GP_BE (group access category forbest effect traffic), AC_GP_BK (group access category for backgroundtraffic), AC_GP_MG (group access category for group management and/orcontrol frames), AC_GP_SEN (group access category for sensors and/ormeters), AC_GP_Emergency (group access category for reporting anemergency, such as fire, intruder detections or patient heart attacks),AC_GP_PS (group access category for power save STAs), AC_GP_LS (groupaccess category for power saving STAs that are long sleepers and strivefor a long battery life) and AC_GP_FILS (group access category for fastinitial link setup, for example for a group of STAs moving together).These access categories may be explicitly or implicitly defined by usinga separate set of local EDCA parameters. In addition, these accesscategories may have higher or lower priority than existing accesscategories.

FIG. 6 is a diagram of an example of group-based channel contention 600.In the example illustrated in FIG. 6, a group-based channel contentionperiod may be preceded by a beacon, a short beacon or other type ofmanagement, control or extension frame 602 in which a base station orWTRU (e.g., an AP) announces a set of WTRUs that are allowed mediumaccess in the coming interval. In an embodiment, the set of WTRUsallowed to access the medium may also be scheduled to wake up at thebeginning of group-based channel contention. In an embodiment, the WTRUsin CGs that participate in group-based channel contention may beassigned to a special interval where other WTRUs are not allowed totransmit. These WTRUs may also conduct group-based channel contention inintervals where other WTRUs conduct normal (e.g., STA-based) channelcontention, with or without different EDCA parameters based on thetraffic priority, STA types, etc.

At the start of a group-based contention period, the contenders for eachCG may start competing for the channel, for example, following normal(E)DCF procedures, either with or without different EDCA parameters. Inthe example illustrated in FIG. 6, after a DIFS period 604 and backoffslots 616, the contender for CG1 gained access to the channel andtransmits its first packet 618 (e.g., UL or peer-to-peer). The firstpacket may be a PPDU of the regular format or a short format. It mayalso include an MSDU, an A-MPDU, or an A-MSDU. The first packet from thecontender may include one or more of the following information in itsPLCP/MAC header, initial scrambling seeds or the frame body: informationabout the CG (e.g., the ID of the CG or order of STAs in the CG), NAVinformation to reserve the medium for the CG1 transmission period 606 orUL or peer-to-peer packets (e.g., PS-Poll or data frames to the AP).

WTRUs in CGs that do not have access to the medium may sleep for aduration of NAV settings included in the first packet from the contenderof the CG that obtained medium access (e.g., the contender for CG1 inFIG. 6). The NAV value may be calculated to be some minimal value sothat the remaining CGs will wake up in time at the end of the current CGtransmission period to prevent much medium idle (and therefore wasted)time.

The CG transmission period for CG1 606 follows the first packet 618 fromthe contender of CG1. After the transmission period for CG1 606 ends,the contenders of the other CGs may wait a DIFS period 608 and thenstart to compete for access to the medium for their respective CGsfollowing, for example, normal (E)DCF procedures, with or without EDCAparameter sets based on the traffic priority, STA types, etc. In theexample illustrated in FIG. 6, the contender for CG5 gained access tothe channel and transmits its first packet 620. The CG transmissionperiod for CG5 610 follows the first packet 620 from the contender ofCG5. After the transmission period for CG5 610 ends, the contenders ofthe other CGs may wait a DIFS period 612 and then start to compete foraccess to the medium for their respective CGs. This time, in the exampleillustrated in FIG. 6, the contender for CG2 gained access to thechannel and transmits its first packet 622. The CG transmission periodfor CG2 614 follows the first packet 622 from the contender of CG2. Thisprocess may be repeated in a similar manner.

FIG. 7 is a diagram of another example of group-based channel contention700. In the example illustrated in FIG. 7, a group-based channelcontention period may be preceded by a beacon, a short beacon or othertype of management control frame 702 in which a base station or WTRU(e.g., an AP) announces the ID of the contender of CG1 or the ID of CG1.The contender of CG1 may start transmitting its first packet 716 a SIFSperiod 704 after the end of the beacon, short beacon or other type ofmanagement, control or extension frame 702. In an embodiment, thecontender for CG1 may also start transmitting immediately at a scheduledstarting time of the group-based channel contention period.

After the transmission period for CG1 706 ends, the contenders of theother CGs may wait a DIFS period 708 and then start to compete foraccess to the medium for their respective CGs following, for example,normal (E)DCF procedures, with or without EDCA parameter sets based onthe traffic priority, STA types, etc. In the example illustrated in FIG.7, the contender for CG5 gained access to the channel and transmits itsfirst packet 718. The CG transmission period for CG5 710 follows thefirst packet 718 from the contender of CG5. After the transmissionperiod for CG5 710 ends, the contenders of the other CGs may wait a DIFSperiod 712 and then start to compete for access to the medium for theirrespective CGs. This time, in the example illustrated in FIG. 6, thecontender for CG2 gained access to the channel and transmits its firstpacket 720. The CG transmission period for CG2 714 follows the firstpacket 720 from the contender of CG2. This process may be repeated atleast until each CG has had a chance to access the medium.

FIG. 8 is a diagram of another example of group-based channel contention800. In the example illustrated in FIG. 8, a group-based channelcontention period may be preceded by a beacon, a short beacon or othertype of management, control or extension frame 802 in which a basestation or WTRU (e.g., an AP) announces the IDs of the CGs as well asthe order of transmission of the CGs. According to the announced order,the contender for CG1 may start transmitting its first packet 816 a SIFSperiod 804 after the end of the beacon, short beacon or other type ofmanagement control frame 802. In an embodiment, the contender for CG1may begin transmitting immediately at a scheduled starting time for thegroup-based channel contention period. At the end of the transmissionperiod of the Nth transmitting CG, the contender for the (N+1)th CG maygain access to the medium when receiving a packet transmitted by a STAin the Nth CG indicating that it is the last packet in the transmissionperiod of the Nth transmitting CG (e.g., setting theend-of-service-period (EOSP) bit in the MAC header to 1 and/or the moredata bit to 0) or through inter-group transmission grant (described inmore detail below). The contender for the (N+1)th CG may starttransmitting a SIFS time after the end of the last packet of thetransmission period of the Nth transmitting CG or a SIFS period afterthe end of the packet including the inter-group transmission grant.

In the example illustrated in FIG. 8, at the end of the transmissionperiod for CG1 806, the contender for CG2 gains access to the mediumwhen receiving a packet (not shown) transmitted by a STA in CG1indicating that it is the last packet in the transmission period for CG1806. The contender for CG2 starts transmitting its first packet 818 aSIFS period 808 after the end of the last packet of the transmissionperiod for CG1 806 or a SIFS period 808 after the end of the packetincluding the inter-group transmission grant. At the end of thetransmission period for CG2 810, the contender for CG3 gains access tothe medium when receiving a packet (not shown) transmitted by a STA inCG2 indicating that it is the last packet in the transmission period forCG2 810. The contender for CG3 starts transmitting its first packet 820a SIFS period 812 after the end of the last packet of the transmissionperiod for CG2 810 or a SIFS period 812 after the end of the packetincluding the inter-group transmission grant. This process may berepeated until every CG has had its turn to access the medium accordingto the announced order.

Once the first packet is transmitted by the contender of a CG, thetransmission period of the CG commences. During the transmission periodfor a given CG, the WTRUs in the CG may access the medium using Intra-CGtransmission grant and surrogate polling.

For intra-CG transmission grant and surrogate polling, it may be assumedthat all STAs in a CG always have a UL packet to transmit. If a CG isformed by WTRUs with positive TIM indications in the beacon or shortbeacons, all WTRUs need to transmit PS-Polls to retrieve buffered DLdata packets. If the CG is formed by WTRUs that do not listen to the TIMindication or beacon, the WTRUs need to transmit PS-Polls to the AP toinquire about the presence of buffered data. If a WTRU in a CG has ULdata to transmit, it may transmit the data to another WTRU or a basestation (e.g., an AP) when it is being polled or has received anintra-CG transmission grant. If a WTRU has UL data to transmit and doesnot belong to a CG, it may compete for medium access using normal DCFprocedures with the same or different ECDA parameters.

The CG transmission period may begin after the contender for a CG (e.g.,STA 1) has transmitted its first packet. This first packet may be one ofmany types of frames, as described above. For example, the first packetfrom STA1 may be a PS-Poll or any other type of UL packet transmitted tothe AP. In response to the first packet from STA1, the AP may transmitone of a DL data packet for STA1, a frame indicating that there is nobuffered packet for STA1 or an ACK frame (in which case the AP maytransmit the DL data packet for STA1 later).

When the AP responds to the PS-Poll or any other type of UL packet fromSTA1 with an ACK frame, the AP may transmit the DL data packet for STA1after a SIFS interval following the ACK frame, in response to which STA1may acknowledge the reception of the DL data packet using frames such asshort ACK, ACK, BA, ACK+Intra-GP-TX-GT (ACK and Intra-Group TransmissionGrant), ACK+SUR-Poll (ACK and Intra-Group Surrogate Poll), data frames,or ACK+EndCGTX (ACK and End-CG-TransmissionPeriod).

When the AP responds to the PS-Poll or any other type of UL packet fromSTA1 to the AP with a frame indicating that there is no buffered packetfor STA1, upon receiving the ACK frame from the AP, STA1 may thentransmit after a SIFS interval an Intra-CG-TX-GT frame to provide anIntra-group transmission grant for the next STA in the CG (e.g., STA2).Alternatively, STA1 may also transmit a Sur-Poll frame to conductsurrogate polling for STA2. If the current STA is the last transmittingSTA in the CG, the STA may then transmit an EndCGTX frame to announcethe end of the CG Transmission Period. Alternatively, if STA1 hasindicated in its first UL packet that it does not have any more ULpackets to transmit, instead of a short or regular ACK or BA, the AP maytransmit an ACK+Poll or an ACK-Intra-GP-TX-GT frame to grant the mediumaccess to the next STA in the CG (e.g., say STA2) to transmit any ULpacket, such as PS-Poll or data.

When the AP responds to the PS-Poll (or any other type of UL packet fromSTA1) with a DL data frame, STA1 may respond with a data frame if it hasmore UL data to transmit or it may acknowledge the reception of DL dataframes with a short or normal ACK or BA if the AP indicates that it hasmore DL data to transmit to STA1. If the AP indicates that it has nomore DL data to transmit to STA1, STA1 may acknowledge receipt of the DLdata frames with ACK+Intra-GP-TX-GT in order to provide an intra-grouptransmission grant to the next STA in the CG (e.g., STA2). STA1 may alsotransmit an ACK+SUR-Poll to acknowledge receipt of the DL data frame aswell as to conduct surrogate polling for STA2. If the AP indicates thatit has no more DL data to transmit to STA1, STA1 may acknowledge receiptof the DL data frames with an ACK-EndCGTX frame in addition toindicating the end of the CG transmission period. In differentembodiments, the transmission order of STAs in a CG may be fixed or maybe rotating according to a pre-arranged or random schedule.

The design of the frames Intra-CG-TX-GT, SUR-Poll, EndCGTX,ACK+Intra-CG-TX-GT, ACK+SUR-Poll, ACK+EndCGTX may be implemented as newsubtypes of management frames, control frames, extension frames or newtype of frames. They may also be implemented as action frames or actionno ACK frames. For example, they may be implemented as an action frameor an action no ACK frame of the type HT, VHT, TV high throughput(TVHT), IEEE 802.11ah, High Efficiency WLAN (HEW), or new type of actionframe. They may also be implemented as a short frame where allinformation is carried in the PLCP header portion.

With respect to Intra-CG-TX-GT frames, these frames may be sent by aWTRU (e.g., aSTA or AP) to another WTRU (e.g., the AP or the next STA(e.g., STA2)) in the CG for which the intra-group transmission grant isprovided. If the frame is the transmitted to the next STA in the CG, theAP may choose to repeat the Intra-CG-TX-GT frame after a SIFS period toprevent hidden nodes in the BSS or OBSS. If the Intra-CG-TX-GT is sentto the AP, it may include an explicit ID of STA2, such as an AID, MACaddress, or other type of ID that the AP and the transmitting STA haveagreed upon, in its PLCP/MAC header, frame body, initial scramblersequence, etc. For example, the ID of STA2 may be included in theAddress 3 and/or Address 4 field of the MAC header. A bit in the PLCP orMAC header (e.g., in the frame control field) may be used to indicatethat Address 3 or Address 4 fields are in use and/or, in combination ofthe frame type/subtype/action frame category field, indicate thataddress 3 or address 4 fields are used for the ID of the STA receivingthe intra-group transmission grant. If the Intra-CG-TX-GT frame istransmitted by the AP, then frames such CF-Poll, PS-Poll, Data+Poll,etc., may be reused as the Intra-CG-TX-GT frame. In response toreceiving the Intra-CG-TX-GT frame from a peer STA in the CG or from theAP, depending on the particular protocol, the STA may start transmittingUL or peer-to-peer frames after a SIFS period. If the Intra-CG-TX-GTframe is received from a peer STA in the CG, and the AP is configured torepeat the Intra-CG-TX-GT, then the STA receiving the intra-grouptransmission grant may only start transmitting a SIFS period afterreceiving the Intra-GP-TX-GT frame from the AP.

With respect to SUR-Poll frames, these frames may be transmitted from aSTA in a CG to the AP to inquire about the presence of any buffered DLframes for another peer STA (e.g., STA2) in the CG. The SUR-Poll framemay include an explicit ID of STA2, such as AID, MAC address, or othertype of IDs that the AP and the transmitting STA have agreed upon, inits PLCP/MAC header, frame body, initial scrambler sequence, etc. Forexample, the ID of STA2 may be included in the Address 3 and/or Address4 field of the MAC header. A bit in the PLCP or MAC header (e.g., in theframe control field) may be used to indicate that Address 3 or Address 4fields are in use and/or, in combination of the frametype/subtype/Action frame category field, indicate that address 3 oraddress 4 fields are used for the ID of the STA for which thetransmitting STA is conducting the surrogate polling. Upon receiving theSUR-Poll for STA2, the AP may start transmitting DL frames for STA2immediately. Alternatively, the AP may first respond with an ACK frameand then start transmitting a DL frame for STA2 after a SIFS time. TheAP may also respond with a frame, such as a poll to STA2 indicating thatthere are no frames buffered for STA2, while allowing STA2 to transmitany UL frames it may have.

With respect to EndCGTX frames, these frames may be transmitted byeither a STA in a CG or by the AP to indicate that the current CGtransmission period ends. This frame may be sent to the AP or may besent to a broadcast or multicast address. It may also be sent to theAP/contender of the next CG functioning as an inter-group transmissiongrant. Upon receiving the EndCGTX frame, the AP and the STAs, as well asSTAs in the CG, will follow channel access rules to compete for themedium.

With respect to ACK+Intra-GP-TX-GT frames, these frames may be largelyequivalent the Intra-GP-TX-GT frames. A difference, however, may be thatthis frame also acknowledges the reception of the frame that is sent tothe transmitting STA immediately before the transmission of theIntra-GP-TX-GT frame. The ACK+Intra-GP-TX-GT frame may also beimplemented in such a way that it includes a block ACK field, similar tothe field in a BA, to provide block ACKs to a sequence of frames sent tothe transmitting STA.

With respect to ACK+SUR-Poll frames, these frames may be largelyequivalent to the SUR-Poll frame. The only difference is that this framemay also acknowledge receipt of the frame that is sent to thetransmitting STA immediately before the transmission of the ACK+SUR-Pollframe. The ACK+SUR-Poll frame may also be implemented in such a way thatit includes a block ACK field, similar to the field in a BA, to provideblock ACKs to a sequence of frames sent to the transmitting STA.

With respect to ACK+EndCGTX frames, these frames may be largelyequivalent to the EndCGTX frame. The only difference may be that thisframe also acknowledges receipt of the frame that is sent to thetransmitting STA immediately before the transmission of the ACK+EndCGTXframe. The ACK+EndCGTX frame may also be implemented in such a way thatit includes a block ACK field, similar to the field in a BA, to provideblock ACKs to a sequence of frames sent to the transmitting STA.

FIG. 9 is a diagram of an example Intra-CG transmission grant andsurrogate polling procedure 900. In the example illustrated in FIG. 9,the contender for a given CG (STA1) may transmit its first packet 908 aSIFS period 904 after the beacon 902. The CG transmission period 906 forthe given CG begins after the contender for the CG (STA 1) hastransmitted its first packet. Here, this first packet is a PS-Pollpacket 902. In response to the first packet from STA1, the AP transmitsa DL data packet for STA1 910. The AP or STA1 then provides anintra-group transmission grant 928 to the next STA (STA2) bytransmitting an ACK+Intra-GP-TX-GT frame 912 to STA2. This frameprovides the intra-group transmission grant to STA2 and alsoacknowledges receipt of the frame that was sent to STA1 immediatelybefore. In response to receiving the ACK+Intra-GP-TX-GT frame 912, STA2transmits its UL data 914 (e.g., after a SIFS period).

The AP may then provide an intra-group transmission grant 930 to thenext STA (STA3) by transmitting an ACK+Intra-GP-Poll frame 916 to STA 3,also acknowledging the UL data 914 transmitted by STA 2 immediatelybefore and polling STA 3 for DL data. In response to receiving thisframe, STA3 transmits its UL data 918 (e.g., after a SIFS period) andalso receives DL data 920 from the AP. STA3 may then provide anintra-group transmission grant 932 to the next STA (STA4) bytransmitting an ACK-SUR-Poll frame 922 to the AP, inquiring about thepresence of any buffered DL frame for STA4 and acknowledging receptionof the DL data 920. In response to receiving the ACK-SUR-Poll frame 922,the AP transmits DL data 924 to STA 4. When this is complete, STA4transmits an ACK+EndCGTX frame 926, acknowledging receipt of the DL data924 and indicating that the CG transmission period 906 ends.

At the end of a CG transmission period, inter-group transmission grantand surrogate polling may occur. Procedures and frame designs forinter-group transmission grant and surrogate polling are similar tothose for intra-group transmission grant and polling.

FIG. 10 is a diagram of an example inter-group transmission grant andsurrogate polling procedure 1000. When the last STA in a CG (e.g., CG1)is transmitting, it may use an EndCGTX+Inter-GP-TX-GT frame or anEndCGTX+ACK+Inter-GP-TX-GT frame to provide an inter-group transmissiongrant to the contender for the next CG (e.g., CG2). In the exampleillustrated in FIG. 10, the contender for CG1 transmitted its firstpacket 1016 a SIFS period 1004 after the beacon 1002, starting thetransmission period for CG1 1006. At the end of the transmission periodfor CG1 1006, the AP or the last STA to transmit in CG1 transmits anEndCGTX+ACK+Inter-GP-TX-GT frame 1018, ending the transmission periodfor CG1, providing the inter-group transmission grant 1024 to thecontender for CG2 and acknowledging a frame received by the AP or lastSTA to transmit in CG1 immediately prior to transmitting theEndCGTX+ACK+Inter-GP-TX-GT frame 1018. In an embodiment, theEndCGTX+Inter-GP-TX-GT or EndCGTX+ACK_inter-GP-TX-GT frame may be sentto the contender for CG2, to an address associated with CG2, such as agroup ID, or to the AP. The AP may choose to repeat theEndCGTX+Inter-GP-TX-GT or EndCGTX+ACK_Inter-GP-TX-GT frame in order toprevent hidden nodes.

In response to receiving the EndCGTX-Inter-GP-TX-GT orEndCGTX+ACK+Inter-GP-TX-GT frame, the contender for CG2 may begintransmitting after a SIFS period. In the example illustrated in FIG. 10,the contender for CG2 transmits its first packet 1020 a SIFS period 1008after receiving the EndCGTX+ACK+Inter-GP-TX-GT frame 1018. If the AP isconfigured to repeat the EndCGTX+Inter-GP-TX-GT orEndCGTX+ACK_Inter-GP-TX-GT frame, the contender for CG2 may begintransmitting a SIFS period after receiving the repeatedEndCGTX+Inter-GP-TX-GT or EndCGTX+ACK_Inter-GP-TX-GT frame sent by theAP. In the example illustrated in FIG. 10, the transmission period forCG2 1010 begins following the transmission of the first packet 1020 bythe contender for CG2.

When the last STA in a CG is transmitting, it may use anEndCGTX+Inter-GP-SUR-Poll frame or an EndCGTX+ACK+Inter-GP-SUR-Pollframe to conduct inter-group surrogate polling for the contender of thenext CG (e.g., CG3). In the example illustrated in FIG. 10, the last STAto transmit in CG2 transmits an EndCGTX+ACK+Inter-GP-SUR-Poll frame1026, ending the transmission period for CG2 1010, providing aninter-group transmission grant to the next CG (CG3) 1030 and inquiringabout the presence of any buffered DL frame for the contender of CG3. Inresponse to receiving an EndCGTX+Inter-GP-SUR-Poll frame or anEndCGTX+ACK+Inter-GP-SUR-Poll frame, the AP may transmit DL frames forthe contender of the next CG or may transmit a frame indicating thatthere are no buffered packets for the contender of CG3. In the exampleillustrated in FIG. 10, after a SIFS period 1012, the AP transmits theDL data for the contender for CG3 1028, beginning the transmissionperiod for CG3 1014. This procedure may be repeated until all of the CGsin the BSS have had a chance to access the medium.

When the AP has detected that all STAs in CG1 have completed theirtransmissions and the AP has no buffered packets for CG1, the AP maytransmit a poll frame or an EndCGTX+Inter-GP-TX-GT to CG2 or thecontender of CG2 to grant medium access to CG2.

The design of the frames EndCGTX+Inter-GP-TX-GT,EndCGTX+ACK+Inter-GP-TX-GT, EndCGTX+Inter-GP-SUR-Poll frame andEndCGTX+ACK+Inter-GP-SUR-Poll may be implemented as new subtypes ofmanagement frames or control frames or as a new type of frame. Inaddition, they may also be implemented as action frames or action no ACKframes. For example, they may be implemented as an action frame oraction no ACK frame of the type HT, VHT, TVHT, IEEE 802.11ah or as a newtype of action frame. They may also be implemented as a short framewhere all information is carried in the PLCP header portion.

The frames EndCGTX+Inter-GP-TX-GT, EndCGTX+ACK+Inter-GP-TX-GT,EndCGTX+Inter-GP-SUR-Poll frame and EndCGTX+ACK+Inter-GP-SUR-Poll mayinclude an explicit ID for a WTRU (e.g., a STA for which the inter-grouptransmission grant is provided or an inter-group surrogate polling isconducted), such as an AID, MAC address, or other type of ID that the APand the transmitting STA have agreed upon, in its PLCP/MAC header, framebody, initial scrambler sequence, etc. For example, the ID of STA2 maybe included in at least one of the address 3 and/or address 4 field ofthe MAC header. A bit in the PLCP or MAC header (e.g., in the framecontrol field) may be used to indicate that address 3 or address 4fields are in use and/or, in combination of the frametype/subtype/action frame category field, indicate that address 3 oraddress 4 fields are used for the ID of the STA for which thetransmitting STA is providing an inter-group transmission grant orconducting surrogate polling.

In an embodiment, inter-group transmission grant and surrogate pollingmay be generalized to STA-based transmission grant and surrogate pollingfor CGs that only include one STA.

Data and frame compression may also be used for STAs within a CG forfurther reduction of transmission overhead. For STAs within a CG, it maybe assumed that they share the security key, and, therefore, they maydecode each other's packets. For STAs in a CG that detect similar data(e.g., sensors that are event-driven and detect events such as fire),repeating the same data (either a fire is detected or not) does notprovide extra information. Instead, the CG may negotiate for acompressed packet format, for example, a same data indication frame,which may be short in length and indicate that the transmitting STAobserves the same data as another STA in the same CG that justtransmitted in the CG transmission period.

When a STA in a CG transmits a frame, another STA that observes the samedata may simply transmit a same data indication frame instead of aregular frame. The same data indication frame may include an identifierof a frame (such as a sequence or a sequence control number) and anexplicit ID of a STA (a STA that transmitted the same data) such as anAID, MAC address, or other type of ID that the AP and the transmittingSTA have agreed upon, in its PLCP/MAC header, frame body, initialscrambler sequence, etc. For example, the ID of the reference STA may beincluded in the address 3 and/or address 4 field of the MAC header. Abit in the PLCP or MAC header (e.g., in the frame control field) may beused to indicate that address 3 or address 4 fields are in use and/or,in combination of the frame type/subtype/action frame category field,indicate that address 3 or address 4 fields are used for the ID of theSTA that observes the same data.

The same data indication frame may be implemented as a new subtype ofmanagement or control frames or new type of frames. In addition, theymay also be implemented as action frames or action no ACK frames. Forexample, they may be implemented as an action frame or an action no ACKframe of the type HT, VHT, TVHT, IEEE 802.11ah, HEW, or new type ofaction frame. They may also be implemented as a short frame where allinformation is carried in the PLCP header portion. In response toreceiving the same data indication frame from a WTRU (e.g., STA1)indicating that STA1 observed the same data that was reported by anotherWTRU (e.g., STA2) in a particular frame, the AP may reconstruct a newdata frame from STA1 by copying the frame body of the particular framesent by STA2.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1-21. (canceled)
 22. A method of transferring small packets in awireless network, the method comprising: generating, by a station (STA),a control frame; on a condition that the STA has data available fortransmission, indicating, in a duration field or via a trafficindication, an estimated time, wherein the estimated time includes atleast a time required for transmission of the data; transmitting thecontrol frame; and receiving a response frame associated with thecontrol frame, wherein the response frame includes a duration field setto a value of at least the estimated time.
 23. The method of claim 22,wherein the control frame is a power save (PS)-poll+buffered traffic(BT) frame or a null data packet (NDP) PS-poll frame.
 24. The method ofclaim 23, wherein if the response frame is associated with the NDPPS-poll frame, the response frame includes an indication to delay accessto a medium by a time period.
 25. The method of claim 24, wherein theindication to delay access resides in a physical layer convergenceprotocol (PLCP) header.
 26. The method of claim 22, on a condition theSTA uses the traffic indication, including 0 in the traffic indication,if the STA has no data for transmission.
 27. The method of claim 22,wherein the response frame further includes an indication of data fortransmission from an access point (AP) to the STA.
 28. The method ofclaim 23, wherein the PS-poll+BT frame or the NDP PS-poll frame isgenerated upon the STA awakening from a sleep state.
 29. The method ofclaim 23, wherein the traffic indication resides in a physical layerconvergence protocol (PLCP) header of the NDP PS-poll frame.
 30. Themethod of claim 23, wherein the time is specified in microseconds, andwherein the duration field resides in a medium access control (MAC)header of the PS-poll+BT frame.
 31. A station (STA) comprising: aprocessor configured to at least: generate a control frame; on acondition that the STA has data available for transmission, indicate, ina duration field or via a traffic indication, an estimated time, whereinthe estimated time includes at least a time required for transmission ofthe data; a transmitter configured to at least transmit the controlframe; and a receiver configured to at least receive a response frameassociated with the control frame, wherein the response frame includes aresponse duration field set to a value of at least the estimated time.32. The STA of claim 31, wherein the control frame is a power save(PS)-poll+buffered traffic (BT) frame or a null data packet (NDP)PS-poll frame
 33. The STA of claim 32, wherein if the response frame isassociated with the NDP PS-poll frame, the response frame includes anindication to delay access to a medium by a time period.
 34. The STA ofclaim 31, wherein the indication to delay access resides in a physicallayer convergence protocol (PLCP) header.
 35. The STA of claim 31, on acondition the STA uses the traffic indication, including 0 in thetraffic indication, if the STA has no data for transmission.
 36. The STAof claim 31, wherein the response frame further includes an indicationof data for transmission from an access point (AP) to the STA.
 37. TheSTA of claim 32, wherein the PS-poll+BT frame or the NDP PS-poll frameis generated upon the STA awakening from a sleep state.
 38. The STA ofclaim 32, wherein the traffic indication resides in a physical layerconvergence protocol (PLCP) header of the NDP PS-poll frame.
 39. The STAof claim 32, wherein the duration field resides in a medium accesscontrol (MAC) header of the PS-poll+BT frame.
 40. An access point (AP)comprising: a processor configured to at least: receive, from a station(STA), a control frame, wherein the control frame comprises a durationfield or a traffic indication indicating an estimated time, wherein theestimated time includes at least a time required for transmission of thedata; in response to the received control frame from the STA, generate aresponse frame comprising a response duration field set to a value of atleast the estimated time; and a transmitter configured to at leasttransmit the response frame.
 41. The AP of claim 40, wherein the controlframe is a power save (PS)-poll+buffered traffic (BT) frame or a nulldata packet (NDP) PS-poll frame,
 42. The AP of claim 41, wherein if theresponse frame is associated with the NDP PS-poll frame, the responseframe includes an indication to delay access to a medium by a timeperiod.